OBJECTIVE: To assess the possible relationship between major depression (MD) and nocturia. SUBJECTS AND METHODS: An unselected group of adult men and women, living in the city of Ostersund, Sweden, were sent a postal questionnaire containing questions on somatic and mental health, sleep, sleepiness and nocturia. For depression diagnostics the Major Depression Inventory (MDI) was used. RESULTS: The mean (sd) ages of the men and women were 48.0 (18.2) and 50.1 (19.1) years, respectively. Two or more nocturnal micturition episodes occurred in 15.6% of the men and 16.5% of the women. In a multiple logistic regression analysis independent correlates (with 95% confidence intervals) for >/= 2 nocturnal voids in men were: MD 6.5 (2.6-15.6); health, fair vs good, 1.8 (1.0-3.9); health, poor vs good, 2.7 (1.1-4.8); age, 60-74 vs 18-29, 3.6 (1.5-8.4) and age >/= 75 vs 18-29 6.7 (2.6-17.4); and in women: MD 2.8 (1.3-6.3); health, fair vs good, 1.9 (1.1-3.2); health, poor vs good, 4.3 (2.6-8.2); age, 60-74 vs 18-29, 3.8 (1.8-7.8), and age >/= 75 vs 18-29, 8.6 (4.0-18.6). Age